1. The Field of the Invention
The present invention relates to methods and apparatus for a catheter provided with a plurality of valves in a single lumen, the valves comprised of linearly extending slits through the catheter wall. In particular, the preferred embodiment of the invention relates to methods and apparatus for intravascular catheters provided with a pair of axially and longitudinally displaced two-way, three-positioned slit valves, one of the pair of valves preferably opening to aspirate or infuse at a predetermined pressure differential applied to the catheter lumen, the second of the pair of valves acting as a surrogate to the first valve should the first valve fail to operate properly.
2. The Background Art
The aspiration and infusion of fluids to a patient's body through a catheter is vital to the patient's well-being. The deprivation of necessary body fluids, medicines, and the like can result in severe damage to a patient's health. Therefore, the most efficient and safe way to aspirate or infuse fluids into a patient through a catheter is an area which requires close attention.
An essential feature characterized by all catheters employed for aspiration or infusion purposes is some type of opening through which fluids may travel. Because of the tubular connecting structure of catheters, such an opening is provided by the inner lumen of the catheters which can usually be accessed at the distal and proximal ends of the catheter. The opening allows fluids surrounding the catheter to be aspirated, and the opening allows medical personnel to infuse fluids through the opening to the same areas that may be aspirated.
The desirability of employing such an opening, however, is lessened due to the continual communication between the catheter and the body cavity of the patient. At some points, such as the withdrawal of blood, it is necessary to bar the flow of fluids to or from a patient. Although physically clamping the catheter to prevent fluid flow therein is possible, the physical manipulations necessary are undesirable due to the constant attention the clamping and unclamping would require. In addition, the physical manipulations are undesirable because of the weakening and wear which would be caused on the catheter.
Recently, those in the art have proposed placement of a valve in the wall of a catheter to bar the flow of fluids to or from a patient through the catheter. The valve, preferably a slit valve formed in the wall of the catheter, usually remains in a closed position with adjacent edges of the valve (e.g., slit) abutting each other. Nevertheless, the adjacent edges may separate in response to a predetermined pressure differential, thus permitting fluid flow through the catheter.
If a predetermined positive pressure differential between the inside and outside of the catheter is exceeded, fluids travel down the catheter lumen, from the inside of the catheter lumen, through the valve to the patient. If a predetermined negative pressure differential between the inside of the catheter is exceeded, fluids travel from the patient to the catheter.
The placement of a slit valve in the wall of the catheter, however, risks the loss of the structural integrity of the catheter. A slit valve increases the flexibility and movement of the catheter wall. The loss of structural integrity is magnified by the number of slit valves placed in the wall of the catheter.
As a result of this loss of structural integrity, catheters containing more than one slit valve were unable to maintain the required degree of catheter tip structural integrity. The increase in the number of slit valves increased the flexibility and movement of the wall of the catheter, and the combination of a number of slit valves has led to the collapse of catheters. Such collapse of catheters prevents aspiration or infusion of fluids from the catheter through the valve.
The collapse of a catheter upon itself, and other catheter-related problems, may seem correctable due to the temporary nature of some catheters. Nevertheless, some catheters, such as long-term indwelling catheters, may potentially be implanted in a patient for several months or years. Simple structural flaws in such catheters can cause unique problems to those particular types of patients using these catheters where it is critical to consistently keep the catheters operating for the well-being of the patient.
Since the introduction of catheters containing multi-position-type slit valves, a relatively low, but constant, level of adverse comments have been received from users about the reliability of these slit valves. During infusion, the lips of the slit valve open outwardly into the blood vessel of the patient permitting fluid to flow through the catheter and into the blood vessel. While functioning successfully to transmit fluids into the body of the patient, unless the slit valve is placed at the most distal point of the catheter, an area exists at the end of the catheter which cannot be cleared of infused liquid. This "dead space" may be an area where a clot may form and/or microorganisms may grow and become a source of contamination; hence, to avoid dead space, the location for placing the valves in the wall of a catheter is severely limited.
Difficulty has also been reported in that multi-position valves may not be able to function consistently for aspiration purposes, particularly when the catheter has been implanted for a long period of time. There are two likely explanations for the cause of such partial dysfunction. A thrombus may have formed over or adjacent to the single slit valve. This could impede the inward opening of the slit valve lips, while enabling them to open outwardly.
An alternative situation is that the side of the catheter in which the slit valve is formed may occasionally come to rest against or in close proximity to the wall of the blood vessel in which the catheter tip is disposed. Under such conditions, any attempt to draw blood inwardly through the slit valve draws the catheter against the wall of the blood vessel, thereby preventing free aspiration. Under such circumstances, infusion would remain unaffected.
Blockage of the multi-position valves can lead to problems other than the prevention of free aspiration. Some medical personnel may attempt to dislodge the catheter from the blocking surface by increasing the pressure on the lumen of the catheter. Such attempts can potentially cause damage to the tissues adjacent the blocking surface which are susceptible to pressure differentials.
In any event, blockage of the multi-position valves, or the incidence of infection caused by contamination of the dead space, usually requires the replacement of the catheter from catheter technology allows medical personnel to replace catheters that have become obstructed or contaminated, such a result is impractical. Unnecessary time and energy spent replacing catheters, not to mention the discomfort experienced by patients during catheter replacement, are problems which should have been compensated for by catheters available according to current existing standard practices.
A need, therefore, exists in the art for a catheter having a plurality of valves, at least one of the valves preferably operating during infusion or aspiration, but the others capable of operating, or acting as a surrogate, should the preferred valve become occluded.
Also, a need exists in the art for a catheter having a plurality of valves that allows preferred operation of a distal valve in relation to any proximal valves during infusion and flushing to minimize the remainder of infused fluids in the lumen of the catheter.
Additionally, a need exists in the art for a catheter having a plurality of valves such that the valves are located so as not to destroy the structural integrity of the catheter, particularly at the distal end of the catheter.
Further, a need exists in the art for a catheter having a plurality of valves which will have the capability of placing and using the catheter without a major deviation from currently existing standard practices.
Still further, a need exists in the art for a catheter having a plurality of valves wherein the plurality of valves operate at the positive and negative pressure differentials applicable in single-valve catheters.